Dehydrating apparatus



Jgm. 22, 1935. e. D. ARNOLD DEHYDRATING APPARATUS Filed March 1, 1950FIG. 1.

3 SheetsSheet 1 Q) RQ Jan. 22, G, D A N DEHYDRAT I NG APPARATUS FiledMarch 1, 1950 3 Sheets-Sheet 2 M Z1440 M244 Patented Jan. 22, 1935UNITED STATES PATENT OFFKIE DEHYDRATING APPARATUS Gerald D. Arnold,Galesville, Wis.

Application March 1, 1930, Serial No. 432,366

13 Claims. (Cl.34-5) This invention, relates to improvements incompactness and that arrangement of the parts dehydrating apparatus.This application is a of a complete and self-contained unit which willcompanion to my application filed August 31, permit of the unitarytransportation of complete 1928, Serial No. 303,158. dehydratingapparatus.

It is a primary object of the present invention It is a furtherimportant object of the invention 5 to provide a drier which willeconomically handle to provide a set of controls by which temperaturelarge quantities of material and rapidly dehydrate and the admission ofair and the rate of feeding such.material with a minimum expenditure ofthe green material to the apparatus are autoenergy, 7 matically governedwith the degree of sensitive- 10 More specifically stated, I propose touse relaness which is necessary in order to secure uniform 10 tivelylarge volumes of heated air and gas in the output of high quality.Uniformity is very much dehydrating operation, to ,convey pneumaticallyto be desired and it has not been wholly achieved the material to bedehydrated through a chamber by hand methods of control, partly becauseof of increasing cross section through which the slowness of responseand partly because of lack l5 material can only move when it isdehydrated of accuracy. By the means hereinafter described,

sufficiently to respond to the decreased velocity I have succeeded inobtaining a very high degree of fluid currents; to conduct the entiredehydratof accuracy in control, and a substantially perfecting operationat pressures less than atmospheric; 1y uniform product.

and to operate under such complete control as Finally, where theapparatus herein disclosed to deliver a substantially uniformly driedproduct. is used :f or drying agricultural produce, it is a fur- 20 Itis most important to the achievement of this ther important object toleave such produce with last objective, that all air should be excludedsubstantially its original color, flavor and food from the dryingchamber .other than that purvalue, to a degree not heretofore achievedin any posely admitted thereto and completely subject other dehydratingequipment involving other to control. than laboratory methods. 25

It is a further very important object of the in- In the drawings:vention to provide dehydrating apparatus which Figure 1 is a sideelevation of apparatus emis portable. While the apparatus hereindisclosed bodying this invention, the wall of the drum and is adaptedfor a wide variety of uses and may act a portion of the heating unitbeing broken away upon a wide variety of materials, it is contemtoexpose the interior construction in vertical 30 plated that it willrealize a principal field of useaxial section.

fulness in the dehydration of agricultural prod- Figure 2 is a plan viewof the apparatus shown ucts, and particularly forage crops such as corn,in Figure 1.

alfalfa, grass, peas, soy beans, and the like. The Figure 3 is a sectiontaken in the plane indicated transportation of such crops is frequentlyneedat 33 in Figure 1.

lessly expensive because of the large volume of, Figure 4 is a sectiontaken on the line 4-4 in and weight of, the water contained therein. ByFigure 1.

dehydration in the field or near the field where Figure 5 is a diagramof the system of controls.

the crop is grown, much of this expense is saved Figure 6 is an enlargedfragmentary detailand the dehydrated product retains .all of the showingin section a part of the supply conduit 40 qualities and advantages ofthe natural crop inand a part of the drum at the point of communicludingcolor, taste, nutrition and vitamin concation therebetween, andillustrating the gasket tent. More particularly, however, the feature ofby which undesired air is excluded from the drum portability makes itpossible to reduce the overnotwithstanding its rotation respecting thesuphead of an expensive piece of equipment such as ply conduit. 45 theapparatus herein disclosed, ,by keeping it sub- Like parts areidentified by the same reference stantially constantly in operation atdifierent characters throughout the several views. points. It may beused, for example, to dehydrate The entire apparatus is assembled upon aa whole succession of crops for a number of difwheel supported frame 10,of which the tongue ferent farmers, and it may also be used to dry 11may be drawn by a tractor to pull the appa- 50 pea vinery waste inaccordance with the disratus from place to place. The dehydratingclosure of the companion application above remechanism will bedescribedin the order of travel ferred to, and the waste of corn andcabbage of material through the machine, after which I canningfactories, and others. The present inshall describe the actuatingconnections and vention therefore seeks to achieve that degree ofcontrols.

Feeding device The previously comminuted material is deposited in thehopper 15, the bottom of which comprises a conveyor 16 operating in theconveyor trough made up of sections 1'7, 18, and 19. The varioussections are hinged together and may be drawn upwardly by means of cable20 to the collapsed position indicated by dotted lines in Fig. 1. Thefact that the hinge between sections 18 and 19 is located at the uppersurface of such sections, and the hinge between sections 17 and 18 islocated at the lower surface of these sections, results in equalizingthe tension and slack produced in the conveyor stretches by hingedcollapse of the trough.

It is immaterial how the comminution wet material is accomplished.Preferably it will be cut up in the field into small pieces at the timeof harvesting, thereby facilitating transportation to the machine. Thematerial may, however, be harvested in the usual manner and delivered toan ordinary ensilage cutter which discharges directly into the hopper15. r In any event, the material is preferably chopped up into smallpieces prior to delivery to the hopper, so that the cut ends of thematerial will expose their water content to the action of the dryinggases. If, however, some grain or malt, or like material is to be dried,it will merely be dumped in the hopper without comminution.

The forward wall of the hopper comprises a gate which is shown in dottedlines at 21 in Fig. 1, and may be adjusted vertically by means of thescrew 22 operated by hand wheel 23. Clearance between this gate and theconveyor 16 will determine the depth of material which will pass fromthe hopper upon the conveyor'apron. This depth will be controlled bymanually varying the position of gate 21 in accordance with the kind ofmaterial to be dried. It will be obvious the this apparatus constitutesa means for regulating the rate of feedingthe dehydrating appa-. -ratus.If the material is wet, it will be desirable to reduce the thickness ofthe layer thereof on the conveyor inorder not to feed the machine toorapidly. If, on the other hand, the material is relatively dry, the gate21 can be raised to allow a relatively thick layer of material to passupwardly on the conveyor.

- At its upper end the conveyor 16 discharges into a throat 25 throughwhich delivery of-the green material is controlled by means of a rotaryvalve 26. This valve cuts off direct communication with the outer airand thereby prevents air from entering in any substantial quantitieswith the material to be dried. The rate of rotation of the valve will beso determined that the valve will carry away the material atsubstantially the exact rate at which it is delivered into the throat 25by the conveyor.

Source of hot gases The material discharged by the valve 26 falls into astream of heated gases traversing the feeding nozzle 27 which leads fromthe mixing chamber 28 into the central compartment of the drum 30, laterto be described. The movement of gases through nozzle 27 is producedsolely by the partial vacuum or depression existing within the drum, dueto the action of a powerful exhaust fan at its outlet end. The gasesutilized include such air as is admitted through the port 31 under thecontrol of door 32, together with the products of combustion incidenttothe burnof the ing of fuel in one or more combustion chambers. of whichtwo are illustrated at 33.

While coal or any other solid fuel may be utilized for the purposes ofthis invention, I prefer for several reasons to use oil or gas. Thehydro-carbon furnaces illustrated in the drawings are not onlyeflicient, but minimize the size of the heating plant, and their outputis virtually free of sufficient quantities of soot and odorous vapors toaffect the appearance or taste of the material to be dehydrated.

The two combustion chambers 33 are substantially cylindrical, and therespective fuel nozzles 34 are arranged tangentially as shown in Fig. 1.The products of combustion will travel helically through the respectivecombustion chambers toward the mixing chamber 28, which they reachthrough the openings 35 in the partition walls 36. In the mixing chamber28 the products of combustion are mixed with the air, if any, admittedthrough door 32.

The diameter of the feeding nozzle 2'7 will be so determined withreference to the capacity of the machine, that the velocity of gasestherein will at all times be sufficient to project the wet materialsupplied through throat 25 pneumatically into the interior of drum 30.The drum is so arranged, however, that the velocity of gases passingtherethrough is reduced repeatedly. The

structural organization of the drum is so important to the successfuldehydration of material passing therethrough, that it will be describedin some detail.

The dehydrating drum The drum 30 is a boiler-like structure mounted toturn as a unit upon the wheels 38 which turn with shafts 39 extendinglongitudinally of frame terial enters by means of nozzle 27. Itterminates in spaced relation to a disk-like baffle 43 which is spacedfrom the opposite end of the drum and closes the end of the intermediatetube 41. The intermediate tube in turn is spaced from the front end ofthe drum as shown at the left in Fig. l. A series of radial struts 44braces the several tubes from each other to make a rigid assembly.

The rigidity of individual tubes is enhanced by longitudinally extendingflanges which may be forwardly inclined in the direction of drum r0-tation, as shown at 45, or may be radial as shown at 46. These flangesact as pockets to lift the green material to the top of the respectivedrum. and to drop it into the path of the gas stream traversing thedrum. It will be understood that the gas entering through nozzle 2'7passes the whole length of the innermost tube 40, is turned by bafile43, and passes toward the front of the machine the whole length of theintermediate tube 41; and is turned by the front end of the drum andpasses to the back end of the machine Means for handling driedniaterials It will be obvious that the weight of the material to bedried will be reduced proportionately to the amount of water extractedin the drying operation. The amount of water in materials ordinarilydried is generally from 50% to 85% of the total weight of the material.Consequently each particle of material undergoes a very great change inweight as it progresses through the machine. This fact is utilized tocontrol automatically the time for which the various particles remain inthe machine. V

When the blast of hot gases entering through nozzle 27pneumatically-projects the green material into the inner tube 40 of thedrying drum 30, the weight of the various particles of material to bedried causes them to drop to the bottom of the tube. particles arecarried by flanges 45 to the top of the tube where they fall from theflanges through the blast of hot gases. Naturally, the lighter particleswill be advanced along the drum by the blast of gases more rapidly thanwill be heavier particles. This is very advantageous because the gasesat this point are at'maximum temperature (averaging about 1000 or 1500degrees Fahrenheit, although a great range of temperatures ispracticable above and below the points specified) and prolonged exposureof minor particles of forage to such high temperatures would bedeleterious, and would result in too great a drying action,notwithstanding .the fact that no material oxidation could occur becauseof the almost complete absence of oxygen.

The amount of air admitted through door 32 is not suflicient to supportcombustion, and the air admitted through the burner ports 34 delivers upsubstantially all of its oxygen for the combustion of the hydro-carbonfuel. Even though combustion of the materialto be dried is impossible,

therefore, it is an advantage to have the very small and light particlesof such material move through the machine more rapidly than the heavierparticles, and this occurs automatically as the particles aresuccessively dropped across the path of the blast of gases.

The rate of evaporation from all of the particles will be very high dueto the tremendous volume of very dry gases to which the particles areexposed, and due also in large part to the fact that the pressuresexisting in the drying drum are sub-atmospheric. The material in itswettest form is exposed to the gases when they are hottest and driest.The relatively large quantity of moisture, and also the high velocityand rapid reduction of temperature, keep the material from burning andflavor change in the presence of heat which would be excessive upondrier material or for longer periods.

It will be noted that no ,blower is employed at the inlet end of thedevice, except that which supplies the air blast required for theparticular oil burners illustrated. The current of gas through thepassages of the drying drum or chamber is created almost solely by theaction of the exhaust fan at the outlet.

As the particles of average size and larger In the rotation of thetube-these,

deliver up their moisture, they too become light and move more and morerapidly through. tube 40, until ultimately a continuous stream ofmaterial is being delivered from tube 40 intothelarger concentric tube41.

The diameterof tube 41 is so much greater than that of tube 40 that thevelocity of the current of drying gases therethrough ismateriallyreduced. Another factor contributing to the reduction of gas velocity inthe successivetubes of the drum, is the decrease in temperatureoccasioned by the evaporation of moisture. It will be noted that thereis very little heat loss by radiation in this device, due to the factthat the outer compartment thereinis in a position to intercept any heatradiating from the two inner compartments. I By the time the gases reachthe, outer compartment, their temperature is very much reduced so thatthe high radiation loss which would occur if the outer shell were filledwith gas at the original high temperature, is quite largely avoided.

In the intermediate shell and the outer shell, as well as in the innershell or tube 40, the rotation of the drum is continually carryingmaterial to the top thereof and releasing it to fall through the gascurrents to the bottom. In practice, the material is not discharged allat once but commences to drop about 120 before reaching the extreme topand continues to be discharged until well past the topposition, whenproperly designed bucket flanges are used. In

the outer chambers this results in discharging material on both sides ofthe central tube or shell, as well assifting down over the relativelyhigh temperature inner shell.

In each such cascade of partially dried material the lighter (andconsequently the most highly dried) particles will move most rapidlywith the air blast. As a result of this factor there is a tendency forall material to leave the machine as soon as it is fully dried, and theresult tends strongly to equalize the extent to which all particles ofmaterial issuing from the machine are dried.

From the outer compartment within the exterior shell 42 of the dryingdrum, the dried material and stream of gases passes centrally about thebaflle 43and through the outlet passage 47 which is laterally extendedat 49 to the axial inlet of the fan casing 50. This fan must besufficiently large and powerful to produce the desired current of gasthrough the drum 30.

Its tangential delivery spout 51 discharges into a pipe 52 which leadsacross the front of the machine to the top of an ordinary centrifugalseparator 53 into which the gas and material is delivered tangentiallyto effect the separation thereof by the vortex thus created within theseparator. The water laden gas then issues from the opening 54 atthe-top of the separator. It will be found that the gas will bevirtually saturated at its discharge temperature if the various factorsrelating to efflcientdrying have been properly worked out in accordancewith the considerations hereinafter explained.

The dried material drops through the bottom opening 55 in the separatorinto the receptacle 56 at the inlet of a pneumatic conveyor fan 57. Thisfan may comprise an ordinary centrifugal blower of which the dischargepipe 58 may lead to a silo, bin, bagging machine, or any otherobjective.

While all the particles of material issuing from the machine will bemore or less uniformly dried to approximately the same degree for thereasons above explained, this degree of dryness may vary in accordancewith a large number of factors in-.

eluding particularly the temperature, dryness, and rate of flow of thegases passing through the drying drum, the rate at which wet material issupplied through the machine, and the degree of wetness thereof, andalso the temperature and. the extent to which the natural juices of thematerial are exposed for evaporation.

Those skilled in the art will perceive that for any given gas conditionsand kind of material,

- the amount of water which will be extracted by the dehydratingapparatus will be a relatively fixed quantity, and consequently thedryness of the discharged material may depend directly upon the rate atwhich the material is fed to the machine. Particularly if the rate offeeding ex-' ceeds the capacity of the machine for extracting moistureto the desired degree of dryness, the product may not be sufficientlydehydrated. The effect of the incoming material is almost immediatelymanifested in reduction of the temperature of the gases supplied fromthe mixing chamber 28, both by direct absorption of heat by the.

material itself, and by the evaporation which occurs in proportion tothe presence of quantities of wet material. I

In view of the foregoing considerations, it is very important in amachine of this character to feed the machine in such a way that therate at which wet material is supplied thereto, can be maintained almostperfectly uniform for any given condition. It is also desirable to beable to vary the rate of feeding instantaneously to correct any factorstending to upset the balance which has been found to give the desireddehydration. The feeding conveyor andleveling gate 21 have been foundvery satisfactory for maintaining a uniform rate of feeding. Thecontrols and driving connections now to be described may be set to careautomatically for any matters requiring correction to produce auniformly satisfactory product.

Driving connections It is contemplated that the dehydrating apparatuswill be driven from the tractor which pulls it from place to place. Inthe dehydrating apparatus the source of power is the pulley .60 onblower shaft 61. From this shaft a belt 62 drives the blower 63 whichsupplies an air blast through pipes 64 to the two burners, the blast ofeach burner being individually controlled by the gate 65 appearing nearthe burner in Fig. 1. It would not be impractical to control the burnersautomatically by the same means hereinafter described, but ordinarilythis is unnecessary for reasons hereinafter mentioned.

Shaft 61 also drives, by means of a belt or chain 70, the runner of theblower fan 5'7 and, on the same shaft, the oil pump 71 which comprises agear pump illustrated diagrammatically in Fig. 2, and shown moreparticularly in Fig. 5.

From the primary driving shaft 61 a chain '72 drives a jack shaft 73from which another chain 74 drives one of the longitudinally extendingshafts 39 for the support and drive of the drum. Chain 75 connects thetwo drum driving shafts so that the respective rolls 38 turnsimultaneously in the same direction to rotate the drum.

Power for the operation of the rotary valve 26 and the conveyor 16, istaken from one of the shafts 39 as shown in Fig. 2. A chain '77 leadsfrom shaft 39 to the driving shaft of a commercial rate changing device78, of which the power output shaftis connected by chain '19 with theconveyor drive shaft 80. The shaft in turn is connected by chain 81 withthe rotary valve. This arrangement insures that the rotary valve willoperate as rapidly as-material is supplied thereto, and it provides forsimultaneous variation in the rate of operation of the conveyor and.valve in accordance with the adjustment of the rate changing mechanismdesignated in its entirety by reference numeral 78.

The system of controls Oil contained in the supply tanks 85 is utilizedfor controlling the operation of the dehydrator, as well as forsupplying the burners 34. The use of two separate tanks is merely forconvenience in positioning the feed conveyor trough, and the two tanksmay function as one, being interconnected. -The oil supply line 86 runsthrough a filter 8'7 and the intake side of pump 71 from which the oilis discharged at relatively high pressure. The pressure usedcommercially in this particular apparatus amounts to fifty pounds. Thispressure is maintained by a loading valve 88 in a by-pass line 89 aroundthepump, so that any'excess of pressure will leak through the by-pass tomaintain the pump output uniform at fifty pounds.

From the output of the pump a high pressure line 90'leads' to theburners 34 where air, supplied through pipe 64', is carbureted anddischarged for combustion into the chambers 33. The helical path offlame and gases in the combustion chamber insures a sufficient length oftravel so that thorough combustion may result before the products ofcombustion pass through the foraminous walls 36 into the mixing chamber28.

From the pump another high pressure line 91 leads to the reducing valve92, where the pressure is reduced sufficiently so that it can be handledby the thermostatically controlled valve 93.

I have found, and it is important to note here, that in normal operationof the device herein disclosed, the dryness of the finished product willbe substantially directly proportioned to the temperature of the gasesat the outlet end of the machine. If this temperature rises too high, itwill invariably be found that the finished product has been toocompletely-dried. If this temperature drops below a proper value, itwill be found that the material is not sufficiently dry.

, Accordingly, I employ at 93 a commercial thermostatic valve mounted onthe exhaust passage 49 to respond to gas temperatures therein. There isan adjustment at 94 whereby the valve may be set to operate at anydesired exhaust gas temperature. This is important, because differentproducts require dehydration to different degrees, and the adjustment at94 enables the operator to secure exactly the desired dehydration. Inpractice fifteen pounds pressure is delivered from the reducing valve 92to the thermostatically controlled valve 93. In the operation of theparticular thermostatic valve shown at 93, there is a certain amount ofwaste oil which is by-passed through pipe 95 to the pump inlet. Theoperationof the thermostatic valve is such that pressure establishedbeyond the valve when the valve is open, is relieved through the pipe 95upon the closing of the valve.

When the thermostatically controlled valve 93 is open, oil pressure iscommunicated through the low pressure line 96 to the damper control 97by means of which the door or damper 32 for admitting fresh air into themixing chamber 28,

is operated. A tension spring 98 normally holds the damper closed, butis overcome by oil pressure when the thermostatic valve opens.

A branch pipe 99 fromflthe low pressure line 96 leads to the pressureoperated controller 100 of valve 101. This valve is located in the highpressure branch '102 of line 90, and leads to a pressure operatedcontrolling device 103 for the rate changing mechanism 78. In order torelieve the controlling device 103 of pressure established therein whenvalve 101 is opened, I provide a bypass valve at 104 which is constantlyopen, and through which a small quantity of oil leaks at all times frompipe 105 to the supply main 86. I

The control apparatus is preferably not of the type which isalternatively in its extreme positions. n the contrary, the apparatusdisclosed will maintain at all times a graduated rate of feedingmaterial and air, which is directly in accordance with the requirementto produce a uniform temperature and hence a uniform product at thedelivery end .of the drum.

It will be noted that the burners may, if de-' sired, be set manuallyfor operation at maximum efilciency and continue at all times in suchoperation without automatic control, although obviously this may be usedwhen desired. In the present apparatus temperature control is effectedwithout any manipulation of the burners whatever. When the temperaturerises in the outlet passage 49, the motion of the feeding conveyor androtary feeding valve is accelerated, thereby immediately increasing therate at which. green or wet material is supplied to the apparatus. Thisin itself will frequently constitute a suflicient regulation to insureuniform output, but in order that the thermostat 94 may immediatelyrespond to the changed situation, I prefer to use also the damper 32which is opened simultaneously with the acceleration of the feedingconveyor. The influx of cold air, while relatively small in volume ascompared with the hot gases delivered to the mixing chamber 28 by theburners and associated mechanism, will immediately temper such gases,and inasmuch as it takes only a fewsecends for gas to pass through theapparatus from inlet to outlet, the result of the tempering willimmediately become effective on the thermostat and tend to preventover-control.

It is very important to note, also, that the influx of air throughdamper 32 accelerates the gas current through the drum so that I notonly temper the heat but increase the speed at which the material moves,thereby decreasing the period of about three minutes for which materialof average weight remains in the drum.

In order to exclude extraneous air and thus enable the accuratefunctioning of the controls above mentioned, I not only pass the greenmaterialthrough the rotary feeding valve 26, but I also provide aninexpensive but relatively airtight joint between the rotating drum andthe feeding nozzle 27 at one end, andthe discharge pipe 47 at the other.The feeding nozzle and discharge pipe have annular flanges as shown at110 in the detail view in Fig. 6. Obviously, these flanges arenon-rotatable. Their exterior faces are preferably disposed insubstantially the exact plane of the respective heads of the drum.

Secured to each drum head is an annular gasket 111 which may be made ofasbestospaper, preferably of the heavy sort used in brake and clutchlining. lIhe depression existing within the drum causes air pressure onthe annular gasket 111 to hold the gasket tightly in contact with theannular flange 110 with respect to which it rotates. As a result, air isvirtually completely excluded from passing through this joint,

and the amount of friction involved is negligible. The life of thegasket is long, and replacement thereof is easy. 1

Dimensional we While those skilled in the art will be able to utilizethe proportionate dimensions of parts illustrated in the accompanyingdrawings as a basis for the manufacture of devices embodying theinvention herein disclosed, it may be useful to imately three feet, andthat of the dry feed separator is approximately flve feet.

The main fan is approximately a three foot fan and is operated directlyfrom the driving pul-' ley 60 at an approximate speed of 1150 R. P. M.The drum revolves at approximately 10 R. P. M. The maximum capacityoutput of dry product from such a dehydrating apparatus will beapproximately two tons per hour when the machine is fed with averageforage. The total weight of the apparatus is approximately that ofportable threshing machine equipment. The power required to operate itwill be approximately 30 H. P., as furnished by standard commercialtractors of that rating.

I claim:

l. Dehydrating apparatus comprising the combination with an exhaust fanadapted to establish a current of drying gases sufficient to propel thematerial to be dried, of a drying chamber communicating with the inletof said fan and mounted for rotation, said chamber being interiorlypartitioned to provide a passage extending back and forth therein andincreasing in cross section in approaching said-fan, means in saidpassage for elevating material and,dropping it transversely of thepassage in the rotation of said chamber, a furnace having a fluecommunicating with the end of said passage remote from said fan andmeans for feed ing material to be dried into the current of heated gassupplied by said flue to said passage, subject to the action of saidfan, and means for controlling substantially completely the admission ofunheated air to the current of gas aforesaid, said means comprisinggaskets and complementary parts to which said gaskets are held by faninduced depression in said chamber during the rotation thereof, saidgaskets and parts being relatively rotatable and disposed at the ends ofthe drum about the flue and fan connections thereto.

2. Dehydrating apparatus comprisinga rotatable drum having openings atits ends, relatively stationary inlet and outlet fittings communicatingwith the drum through said openings and air excluding means at each ofsaid openings comprising relatively rotatable annular gaskets connectedat their outer margins to the drum, and flanges carried by saidfittings, and a gas circulating device operatively connected with one ofsaid fittings and adapted to create circulation of gas through said drumand thereby to establish a pressure differential between the interior ofsaid'drum and the exterior atmosphere, said gaskets abutting theirrespective flanges and yieldably subject tosaid pressure differential.

3. Dehydrating apparatus comprising the combination with a rotatabledrum and means for feeding combustible vegetablematerial thereto, of aninlet fitting communicating axially therewith in the path of suchmaterial, a cylindrical combustion chamber communicating with saidfitting adjacent one of its ends and adapted todeliver burnt gasesacross the path of suchmaterial, a checker brick wall providing a porouspartition between said combustion chamber and the point where suchmaterial encounters burnt gases produced in said chamber, a burnerdisposed tangentially in said combustion chamber at a point spacedfromthe point of communication aforesaid, and means for feeding combustiblefuel of proper mixture with air through the burner, wherebysubstantially complete combustion in said chamber is ensured by thehelical travel of burning gases issuing from said burner. 4. A portabledehydrating apparatus comprising the combination,-of a drying drumrotatably mounted and provided with an inlet nozzle at its end, anexhaust fan connected with the other end of thedrum, furnace meansoperatively connected to supply hot gases to said nozzle and a feedingthroat communicating with said nozzle and provided with a conveyor, anda rotary valve for the delivery of substantially air free material intosaid nozzle in the path of gases from said furnace, said furnace meanscomprising a pair of cylindrical combustion chambers disposed atopposite sides of the nozzle and provided at mutually remote points withsubstantially tangential burners whereby to be adaptedto feed productsof combustion in a helical path through said chambers to said nozzle.

5. Dehydrating apparatus comprising the combination with a furnaceadapted to supply a heated gas, of a chamber provided with an elongateddrying passage of increasing cross section connecting at its inlet endto receive gas from the furnace, a conveyor provided with a dischargethroat communicating with said passage and adapted in the operation ofthe conveyor to deliver material to be dried into the path of the heatedgas in said passage, means for exhausting gas from the larger crosssection end of the passage, whereby to pro-- vide in said passage a gascurrent of sufficient proportions to conveypneumatically through thepassage the material to be dried, a thermostat exposed to exhaust gastemperature and actuating connections for the feeding conveyor includinga speed governor operatively connected for regulation by saidthermostat.

6. Dehydrating apparatus comprising the combination of a rotatable drumprovided with a pas sage of increasing cross section and bucket meansadapted to elevate and discharge across said passage the material to bedried, a furnace operatively connected to supply hot gas to the inletend of the passage, an exhaust fan operatively connected to withdraw gasfrom the outlet end of the passage, the current of gas in the passagebeing sufiicient to propel therethrough at a rate dependent upon thedryness of the material and the decreasing velocity of the current, afeeding conveyor adapted to deliver material to be dried into the pathof the gas passing through said drum and provided with a delivery throatcommunicating with the interior of said drum, a thermostat exposed tothe temperature of gas at the exhaust end of said drum and actuatingconnections for said conveyor including regulating mechanism operativelyconnected for control by said thermostat whereby the operation of saidconveyor is made dependent upon the temperature of exhaust gas from saiddrum.

7. Dehydrating apparatus comprising the combination of a rotatabledrumprovided with a passage of increasing cross section and bucket meansadapted to elevate and discharge across said passage the material to bedried, a furnace operatively connected to supply hot gas to the inletend of the passage, an exhaustfan operatively connected to withdraw gasfrom the outlet end of the passage, the current of gas in the passagebeingsuflicient to propel therethrough at a rate dependent upon thedryness of the material and the decreasing velocity of the current, afeeding conveyor adapted to deliver material to be dried into the pathof the gas passing through said drum and provided with a delivery throatcommunicating with the interior of said drum, a thermostat exposed tothe temperature of gas at the exhaust end of said drum and actuatingconnections for'said conveyor including regulating mechanism operativelyconnected for control by said thermostat whereby the operation of saidconveyor is made dependent upon the temperature of exhaust gas from saiddrum, together with means for depositing. a substantially uniform layerof material to be dried upon said conveyor.

8. The combination with a drying chamber and means for circulatingtherethrough a drying medium and the material to be dried, of means forregulating the drying operation in said chamber automatically inaccordance with the temperature of said medium as it leaves saidchamber,,said means comprising a thermostat exposed to such temperature,a feeding conveyor for the material to be dried, actuating connectionsfor said feeding conveyor including a regu-.

lator operatively connected with said thermostat for control thereby, asupply pipe for the drying medium and a damper in said pipe operativelyconnected with" said thermostat for operation simultaneously with saidregulator whereby to temper the drying medium with atmospheric air.

9. Dehydrating apparatus comprising the combination of a drying passage,a furnace operatively connected to supply heated gas thereto and afeeding conveyor for material to be dried, of an exhaust fan connectedto said passage to withdraw the drying gas therefrom, a thermostatsubject to the temperature of the gas withdrawn, a damper for saidfurnace arranged to temper the heat of the gas delivered thereby throughthe admission of atmospheric air to such gas, actuating connections forsaid conveyor including means for controlling the operation thereof andoperative connections between said thermostat, said damper and saidconveyor controlling means automatically adapted to open said damper andsimultaneously to feed additional material to be dried upon a rise intemperature of the discharge gas.

10. Dehydrating apparatus comprising the combination with a rotatabledrum provided internally with flights for the lifting of material to bedried and the discharge of said material transversely of said drum, ofmeans for feeding to the inlet end of said drum material to be dried,means for heating and delivering fresh atmospheric air to said drum,damper controlled means for admitting previously unused fresh air inaddition to that normally heated, whereby to reduce the temperature ofthe air admitted to the drum and increase its volume, and suction meansapplied to Slid drum at a point remote from the point at which saidmaterial enters the drum, said suction means operating at a capacitysuch as to produce a material-propelling current of air through and fromthe drum while maintaining a partial vacuum therein, and means forseparating from the air withdrawn from the drum the material entrainedtherewith, together with a thermostat subject to the temperature of theexhaust air and permanently discharged from said drum operativelyconnected to regulate said damper, the opening of the damper beingadapted not only to reduce the temperature of the air but also toaccelerate the movement of the material through the drum.

11. In a dryer, a. furnace for supplying heated gas previously unused.for dehydration, a drum having a chamber provided with drying passagesof increasing cross-section one of which has its inlet end communicatingwith said furnace, a conveyor communicating with said passage andoperable to deliver material to be dried into the path of the heated gasdelivered to said passages from said furnace, means -for exhausting andpermanently discharging gas from the larger end of another of saidpassages to produce in said passages a gas current of suflicientvelocity to penumatically convey through said passages all of thematerial to be dried, and a thermostat exposed to the temperature of thegases finally exhausted from said passages for controlling the operationof said conveyor.

12. In a dryer, a drum forming a drying chamber, suction means forpropelling through said chamber in the same direction both a previouslyunused drying medium and the material to be dried, means for separatingthe medium from the other material and for permanently discharging themedium, and means operable by the temperature of the permanentlydischarged medium for automatically controlling the relative rate oftravel of the material and said medium and thereby controlling thedrying operation within said chamber.

13. In a dryer, a drum forming a drying chamber, a furnace for supplyingheated gas to said chamber for drying purposes, suction means forpropelling through said chamber both the gas from said furnace and thematerial to be dried, means for separating the gases from the othermaterial and for permanently discharging the gases, means operable bythe temperature of the permanently discharged gases for automaticallycontrolling the relative rate of travel of the material and said mediumand thereby controlling the drying operation within said chamber, andmeans operable by the temperature of the permanently discharged gasesfor automatically controlling the temperature of the gases delivered tosaid chamber from said furnace.

GERALD D. ARNOLD.

